1. Field of the Invention
The present invention relates to an apparatus for taking out a molded product by letting the retaining mechanism unit for retaining a molded product penetrate between the die halves after die opening, for instance, in an injection molding machine.
2. Disclosure of the Prior Art
The basic operation of an injection molding machine of the above type is as follows. Resin is injected into a mold cavity subsequently to clamping of the die halves and after the resin has been cooled, the die halves are opened. Thereafter, a molded product is taken out by a take-out apparatus such as a product take-out robot and then, the die halves are again clamped. Such an operation is repeatedly carried out.
Take-out of a molded product is performed by a take-out apparatus for a molded product, which has a retaining mechanism unit for retaining a molded product and a moving mechanism unit for moving the retaining mechanism unit.
The take-out operation of the take-out apparatus for a molded product is carried out in the way shown in FIG. 6. Specifically, after die opening, the retaining mechanism unit which has been stopping at a waiting position (A) penetrates to an penetrating position (B) within the die halves. Then, the retaining mechanism unit moves toward a take-out position (C) and stops upon arrival at the take-out position (C) ({circle around (1)} penetration process). At the take-out position (C), the retaining mechanism unit retains the molded product which has been separated from a die half ({circle around (2)} take-out process). The retaining mechanism unit with the molded product retained moves back to a specified pulling out position (D) from the take-out position (C). After moving to a withdrawing position (E) ({circle around (3)} withdrawal process), the retaining mechanism unit moves from the withdrawing position (E) to a retrieving position (F) where it liberates the molded product and when reaching the retrieving position (F), the retaining mechanism unit stops ({circle around (4)} conveyance process). At the retrieving position (F), the molded product is released from holding by the retaining mechanism unit so that the molded product can be retrieved ({circle around (5)} liberation process). Upon completion of liberating the molded product at the retrieving position (F), the retaining mechanism unit returns from the retrieving position (F) to the waiting position (A) ({circle around (6)} return process) where the retaining mechanism unit waits until the next take-out operation for a molded product starts ({circle around (7)} waiting process).
A time chart for the above processes (see FIG. 7) is constituted by the penetration/withdrawal time Tae (FIG. 7(a)) which is required for the penetration process and the withdrawal process; the conveyance time Tef (FIG. 7(b)) required for the conveyance process; the molded product liberation time Tf (FIG. 7(c)) required for liberation at the retrieving position (F); the return time Tfa (FIG. 7(d)) required for the return process and the wait time Ta (FIG. 7(e)) required for waiting at the waiting position (A).
Conventionally, in the return process in which the retaining mechanism unit which has liberated the molded product returns from the retrieving position (F) to the initial waiting position (A), the returning operation is set by the operator such that the retaining mechanism unit can move as fast as possible. This is because a sufficient wait time is ensured for the retaining mechanism unit when waiting at the waiting position (A) in order that the retaining mechanism unit should penetrate between the die halves immediately after completion of the next die opening thereby executing the penetration process without fail. For completing the return process quickly, it is necessary to increase the moving speed of the retaining mechanism unit, which involves rapid acceleration and rapid deceleration. The moving mechanism unit is therefore activated abruptly, entailing strong impact on the moving mechanism unit. As a result, there arise the problems of damage to the mechanical parts at an early stage and increased electric power consumption.
A prime object of the invention is to reduce damage to the mechanical parts of a moving mechanism unit and electric power consumption in an apparatus for taking out a molded product, the apparatus comprising a retaining mechanism unit for retaining a molded product and a moving mechanism unit for moving the retaining mechanism unit, the apparatus being designed such that the retaining mechanism unit penetrates between die halves from a specified waiting position after die opening to take out the molded product and the molded product is liberated at a specified retrieving position which is located outside the die halves.
The above object can be accomplished by an apparatus for taking out a molded product constructed according to the invention, the apparatus comprising:
time measuring means for measuring return time in a preceding process, the return time elapsing between a start of returning operation in which the retaining mechanism unit returns to the waiting position from the retrieving position and the next start of penetrating operation in which the retaining mechanism unit penetrates between die halves from the waiting position to take out the molded product;
arithmetic means for calculating a return moving speed distribution for a process succeeding the preceding process such that the returning operation is completed upon elapse of the return time measured by the time measuring means; and
controlling means for activating the moving mechanism unit in such a way that the returning operation is carried out in the succeeding process according to the return moving speed distribution.
The above technical means functions in the following way.
In the molded product take-out operation of the preceding process (i.e., initializing operation) which is firstly carried out, the retaining mechanism unit which has liberated the molded product at the retrieving position is moved from the retrieving position to the waiting position by carrying out returning operation with the moving mechanism unit, and the retaining mechanism unit temporarily stops and waits at the waiting position until completion of die opening. At that time, the return time taken for the returning operation and the wait time at the waiting position are measured by the time measuring means, and then, a return moving speed distribution which allows the returning operation to be carried out within the measured return time is calculated by the arithmetic means. The moving speed in the return moving speed distribution calculated herein includes the wait time for the preceding process so that the moving speed can be made slower than that of the conventional system in which a wait time is assured. In consequence, moderate acceleration and deceleration can be carried out in the invention. In the returning operation in the succeeding process which takes place after the preceding process, wait time substantially vanishes because the moving mechanism unit is activated based on an instruction from the controlling means according to the return moving speed distribution calculated by the arithmetic means, so that the activation of the moving mechanism unit at that time can be performed at a moderate speed.
The invention is designed as described above and therefore exerts the following effects.
In the apparatus for taking out a molded product according to the invention, the retaining mechanism unit is arranged such that its moving speed in returning operation is reduced thereby moderating acceleration and deceleration to slowly activate the moving mechanism unit, whereby damage to the mechanical parts of the moving mechanism unit and electric power consumption can be restricted. In consequence, the service life of the apparatus can be prolonged and the cost of electric power consumption can be reduced.
The above object can be also achieved by the arrangement wherein: the retaining mechanism unit takes the molded product out of the die halves and performs conveying operation in which the molded product is conveyed from a specified withdrawing position located outside the die halves to the retrieving position;
the time measuring means also measures the conveyance time required for the conveying operation;
the arithmetic means calculates a moving speed distribution for the conveying operation and a moving speed distribution for the returning operation based on the total time of the conveyance time and the return time; and
the controlling means activates the moving mechanism unit so as to carry out the conveying operation and the returning operation according to the moving speed distributions. This arrangement moderates not only acceleration and deceleration in the returning operation but also acceleration and deceleration in the conveying operation, so that damage to the mechanical parts of the moving mechanism unit and electric power consumption can be further lessened.
Other objects, features, aspects and advantages of the invention will become more apparent from the following detailed description of embodiments with reference to the accompanying drawings and claims.